This invention relates generally to methods and apparatus related to heat induced antigen retrieval systems of biological specimens to protect, preserve, unmask or even enhance antigens or epitopes for further analysis.
Medical analysis of human or animal tissue specimens may include embedding the specimens in paraffin, cutting thin slices from the paraffin blocks, and placing the slices on microscope slides. The specimens are stained for improved viewing under a microscope. For further analysis, immunohistochemistry or similar techniques may be used, wherein monoclonal or polyclonal antibodies are used to identify tumors, infectious diseases, tissue constituents, etc. Some of the specimens may require the application of a heat retrieval method to permit the antibodies or probes access to the targeted antigen/epitope or sequence. The heat retrieval method may include placing a retrieval solution on the slides and heating the slides to between about 80° C. and about 120° C. or perhaps even between about ambient room temperature to about 128° C. in a heating device such as a microwave, steamer, rice cooker, pressure cooker, or autoclave. Using a pressure cooker raises the boiling point of the solution and prevents it from boiling off at maximum cooker temperature, and also speeds up the process. After heating, the slides are removed from the heating device for immunohistochemistry analysis.
A major problem with heating slides in a conventional cooking device such as a microwave or pressure cooker is that the temperature and pressure cannot be monitored for precise and reliable results as well as other system deficiencies including the need for at least some automation. According to laboratory governing bodies that issue operating standards for quality control, such as the College of American Pathologists (CAP), daily quality control measures should be implemented for such laboratory testing. Typical guidelines issued by a governing body are as follows: 1. Laboratory tests using a heating device should have the temperature recorded. 2. Laboratory tests using pressure should have the pressure recorded. 3. The pH of solutions for heat retrieval procedures should be recorded at the temperature used. 4. Any electrical water bath should have a 3-prong power plug.
Conventional cooking devices cannot efficiently measure temperature, pressure, or pH. In the past, if a device does not measure temperature, it cannot be used for complying with laboratory quality control standards. Another problem is that past devices may not automatically adjust the total heating time to compensate for different amounts of materials in the cooker, since more massive contents must be heated longer than with less contents. Additional heating device systems are discussed in U.S. Pat. No. 6,580,056 to Tacha, hereby incorporated by reference in its entirety.